Owing to the recent popularization of portable electric devices, the demand for mold type storage batteries such as nickel cadmium batteries, nickel hydrogen batteries and lithium ion batteries is increasing.
These batteries are manufactured usually by assembling electrodes made by activated material under an electrically discharged condition. Before delivering to customers, the batteries are charged electricity, activated by repeating the charge and discharge of electricity, or voltage or capacity of the battery is inspected by conducting the charge and discharge of electricity.
When a high voltage or a large amount of electricity is charged into a mold type battery or electricity is charged or discharged beyond the capacity of the mold type battery, gases are generated inside the battery, causing the increase of the inner pressure as well as the increase in the inner temperature of the battery. In order to prevent the increase of the inside pressure and temperature at the occurrence of any abnormalities, a safety valve may be provided inside the battery to discharge the generated gases outside to reduce the inside pressure of the battery. However, rapid generation of gases inside the battery may cause splitting of the battery container and spreading of the organic solution used as an electrolyte outside together with the oxygen and hydrogen contained therein. That eventually might cause fire and damage the surrounding batteries and devices.
As a means for charging or discharging the battery, an electrically conductive contact pin freely detachably provided with the charge and discharge device has been used. In order to ensure the contact of the electrically conductive contact pin with the battery electrode, a pressing means such as a spring or a board spring is provided so as to apply a pressing force to the contacting end. The conventional electrically conductive contact pins are also provided with a controlling means which can suspend the electric charge or discharge in the case of any occurrence of abnormalities of the battery at the time of charge or discharge.
For instance, Japanese Patent Laid Open No. 9-204939 discloses a temperature sensor for measuring the battery temperature which is provided inside the electrically conductive contact pin wherein an electricity suspension means is actuated in response to a signal generated from this sensor.
However, the above method of controlling the electricity charge according to the signal of battery voltage, electric current or battery temperature relies on the normal operation of the electric power supply apparatus or controlling apparatus. These apparatuses might work wrongly in case of occurrence of any failure or noise to the apparatus. That results in an excessive charge or discharge of the battery. Therefore, reliability of this method is insufficient.
Further, in order to continuously monitor the condition of a battery by sensing the charge voltage, charge current and battery temperature, many additional means must be provided inside the electrically conductive contact pin as well as another means for processing the information thus sensed. Therefore, owing to the resultant complex structure of the electric conductive contact pin, the reliability of the device is deteriorated and the production cost of the device inevitably becomes high. Further, the cost of the whole apparatus for charging or discharging the battery also becomes high.